Such roll-bar systems are used to protect the passengers in motor vehicles without a protective roof, typically in convertibles or sports cars during a roll-over, so that the vehicle can roll over onto the upwardly projecting roll-bar body.
It is known how to provide a permanently installed roll bar spanning the entire width of the vehicle. In this solution, the increased wind drag and the occurrence of driving noise is perceived as a drawback, apart from impairing the appearance of the vehicle.
It is also known how to assign a so-called constant-height, rigid, vertically upwardly projecting roll bar to each seat of the vehicle. This solution is typically used in sports cars to underscore the sporty appearance, but it is also used in convertibles.
Also widespread in convertibles are structural solutions in which, as an alternative to the rigid roll bars, the roll-bar body is retracted in the normal condition, and in the event of an accident, i.e., during an impending roll-over, it is quickly extended into a protecting position, in order to prevent the passengers from being crushed by the overturned vehicle.
These roll-bar systems typically have a U-shaped roll-bar body or one made of other profiled sections, guided in a guide body fixed to the vehicle, the guide body being secured in a cassette-type housing. This roll-bar body in the normal condition is held in a lower position of rest by a holding device against the biasing force of at least one actuating compression spring, and in the event of a roll-over a sensor releases the holding device and the force of the actuating compression spring can bring it into an upper, protecting position, and then a locking device, or retraction brake, is engaged and prevents the roll bar from being pushed in. This so-called crash drive in the form of the actuating compression spring can also be combined with a continuously displaceable drive, the so-called comfort drive.
Typically, each seat in the vehicle is assigned a cassette, especially the front seats. In the rear, the cassettes can also be integrated in a rear wall structural unit. Such a cassette type construction of a roll-bar system with a U-shaped roll bar is presented, for example, by DE 43 42 400 A 1; an alternative cassette construction with a roll-bar body in the form of a profiled body is shown, in particular, by DE 198 38 989 C1.
The invention is based on the roll-bar system which is rigid relative to the vehicle seats.
Yet in sports cars with retractable roof (top), and also in convertibles in any case, one must take into account the rigid, upwardly projecting roll-bar body, since the top has to travel over it. In particular during the presently popular automatic opening and closing movement of the top, the upwardly projecting roll-bar body must not hinder the path of movement of the top.
But since the height of the roof is limited by reasons of design, as well as engineering (especially the Cw, a drag coefficient value), the height of the roll-bar tangent, dictated by the upwardly projecting dimension of the roll-bar body, is also limited, which necessitates a compromise between the structural requirements, on the one hand, and passenger protection, on the other.
From DE 44 25 954 C1 there is known a roll-bar system for motor vehicles with retractable roof, having a roll bar providing sufficient passenger protection with either an open or a closed roof, and not hindering the path of movement of the roof either when opening or closing, since the roll bar is placed in a lower setting position when the roof is closed and in an upper setting position when the roof is opened, having a lift mechanism provided for the movement of the roll bar between the lower and the upper setting position, being connected by means of a forcible mechanical guidance to the control mechanism provided for opening or closing of the roof.
This known roll bar has the benefits of a rigid roll bar, since it cannot be fully retracted into the car body, but instead can only move between two raised positions, both of which offer sufficient protection to a person situated in the particular vehicle seat. Because the roll bar is in a lower raised position when the roof is closed, it is possible to design a stable and aerodynamic roof, so that the closed roof merges elegantly in the overall vehicle contour and also the somewhat lowered roll bar means that the roof can be drawn more shallowly across the passenger compartment by design. The forcible mechanical guidance of the setting and lifting mechanism accomplishes a forcible linkage between the particular setting position of the roll bar and the opening or closing movement of the roof.
In the known application, the mechanical lifting mechanism for placing the roll bar, accommodated in a sleeve-like stowage, into the two raised positions by means of a bar lever is linked mechanically and frictionally to the control mechanism for the roof movement via a roof lever. The bar lever itself is connected via a transmission rod with a link guidance in the sleeve-like stowage to the roll bar at a link block.
The mechanical lifting mechanism for adjusting the height of the roll bar, i.e., for raising and lowering the roll bar in the vertical plane into the two raised positions and its mechanical coupling to the mechanical forcible guidance mechanism, mechanically actuated by the roof control mechanism, produces a highly complex kinematic construction with high installation and adjustment expense, and what is more it is prone to malfunctions.
DE 600 01 224 T2 shows a roll bar for a convertible with folding roof, not consisting, as is usual, of a naturally rigid single-piece bar, but rather of two bar elements linked at the tips of the bar, the lower free ends of each bar element being able to move between two positions by means of a frictional roller, having an interior thread, along a horizontal slideway by means of a spindle drive, coupled to the roof displacement mechanism. In the first position, the free ends are at a distance from each other, so that the linked connection and thus the tip of the bar is lowered and thus the roof can move freely. In the second position, which is adopted when the roof is opened, the free ends lie closer to each other, so that the bar elements are raised relatively steeply and the bar has the necessary height to provide protection.
However, due to the upper link of the two-element roll bar the strength of the roll bar is quite substantially impaired. What is more, during a roll-over the two frictional rollers with the interior thread in connection to the actuating spindle need to absorb the large forces, which require a corresponding expensive dimensioning of these elements.
DE 197 52 068 A1 discloses a roll-bar system for a motor vehicle with a multipart folding roof, consisting of a front roof element, which is hinged to the car structure and able to fold into a stowage position toward the rear, and a rear roof element, hinged to the rear. The front roof element is pivoted on the car structure by two roof pillars, arranged at opposite sides, and the side roof pillars can be guided further downward via the pivot axes on the car structure to form a roll bar extending across the width of the vehicle with two U-shaped bar segments associated with the seats. The arrangement is such that the roll bar in the stowage position of the front roof element is forced to adopt its upward lying, protecting position.
This known system requires, first of all, a costly roof construction, prone to malfunction, and second, the two linkages of the roof pillars on the car structure must absorb the large forces during a roll-over, which necessitates a correspondingly strong design of the linkage, which can impair the appearance of the vehicle. Moreover, the swivel movement of the roll bar about the transverse axis requires a correspondingly large structural space, which is in scarce supply as it is for vehicles having an open roof.